The present invention relates to a process for producing a pyrrolidone derivative represent by the general formula (I): ##STR2## wherein R is an organic residue obtained by removing hydroxy radical from a C.sub.1-10 primary alcohol, C.sub.1-10 secondary alcohol or derivative thereof, by reacting acetaldehyde with 2-pyrrolidone, thereby containing N-(.alpha.-hydroxyethyl)pyrrolidone and reacting with a primary alcohol, a secondary alcohol or a derivative thereof with the thus obtained N-(.alpha.-hydroxyethyl)pyrrolidone to obtain the object product, the pyrrolidone derivative represented by the formula (I).
N-(.alpha.-hydroxyethyl)pyrrolidone and N-(.alpha.-alkoxyethyl)pyrrolidone are the useful starting materials for the synthesis of N-vinylpyrrolidone along the following reaction formula. ##STR3##
As a process for producing N-(.alpha.-alkoxyethyl)pyrrolidone,
(1) a process for producing N-(.alpha.-ethoxyethyl)pyrrolidone by reacting diethylacetal with 2-pyrrolidone (yield: 34%) (refer to Ber. Vol. 99,2128,1965), and
(2) a process for producing N-(.alpha.-methoxyethyl)pyrrolidone by reacting .alpha.-chloroethyl methyl ether with 2-pyrrolidone (yield: 78%) (refer to Japanese Patent Application Laid-Open No. 56-75464 (1971)) have been hitherto known.
However, these processes are not industrially satisfactory, because the yield of the process (1) is low and the industrial utilization of the starting material of the process (2) is difficult.
On the other hand, a process for producing N-(.alpha.-hydroxyethyl)cyclic amide has been known. For instance, in Japanese Patent Publication No. 45-14283(1970), a process wherein acetaldehyde is reacted with a secondary cyclic amide by liquid-liquid contact in the presence of an acidic catalyst or basic catalyst, thereby containing N-(.alpha.-hydroxyethyl)cyclic amide and the thus obtained N-(.alpha.-hydroxyethyl)cyclic amide is subjected to thermal decomposition to obtain N-vinylamide, has been disclosed.
However, there is a problem in the process that the yield of the thus produced N-(.alpha.-hydroxyethyl)pyrrolidone is low. For instance, Example 3 of the Japanese Patent Publication only discloses the yield of the final product, N-vinylpyrrolidone, however, even in the case where the rate of conversion of N-(.alpha.-hydroxyethyl)pyrrolidone to N-vinylpyrrolidone by thermal decomposition is assumed to be 100%, there is a problem that the yield of N-(.alpha.-hydroxyethyl)pyrrolidone is only about 50%.
As a result of the present inventors' studies concerning a process for producing a pyrrolidone derivative useful for the synthesis of N-vinylpyrrolidone in a higher yield than that of the hitherto-known methods, the present inventors have found that an object of the present invention is easily achieved by (1) reacting acetaldehyde with 2-pyrrolidone in the presence of a catalyst (hereinafter referred to as "the first step"), thereby obtaining N-(.alpha.-hydroxyethyl)pyrrolidone and (2) reacting the thus obtained N-(.alpha.-hydroxyethyl)pyrrolidone with a primary alcohol, a secondary alcohol or a derivative thereof in the presence of a acidic catalyst (hereinafter referred to as "the second step"), and the present invention has been attained based on the above-mentioned finding.